Autonomous Energy Management Strategy in the Intermediate Circuit of an Electric Hybrid Drive with a Supercapacitor

Abstract

Hybrid electric vehicles (HEVs) require the design of an energy management strategy (EMS). Many EMS are solved using different types of deterministic rules (rule-based (RB)) or optimization-based (OB) methods. The disadvantage of these strategies is that the primary energy flows in the drive are only solved “ex post,” when in principle, they cannot bring a substantial increase in energy recovery. A little-studied HEV traction drive topology is an internal combustion engine (ICE), supercapacitor (SC), traction motor (TM), and electric power divider (EPS) assembly. The original EMS method implemented in this assembly is based on the control of energy flows at the physical level in the DC link node. Changes in the power of the TM, under the condition of zero summation of currents in the DC link, will spontaneously induce energy spillover from and to the supercapacitor. The state of energy (SOE) in the supercapacitor can then be maintained by the balanced power of the ICE. This makes it possible to achieve a reduction in accelerations of approximately 30%. In principle, the presented EMS makes it possible to absorb all the kinetic and potential energy of negative driving resistances, thereby significantly reducing vehicle consumption. The strategy does not even require knowledge of the driving profile and bypasses complicated optimization algorithms. When validating the EMS method on an experimental test bench by implementing the driving cycle into real prototype components of the HEV physical model, a recovery rate of 14% was achieved, but the potential is up to twice that.